This invention relates to fluid filter elements, and particularly to filter elements used for filtering particulate contaminants from lubricating oil, fuel, gas, air and other fluids.
Filters for the lubricating oils of internal combustion engines typically use a disposable circular cylindrical filter element which has a perforate central core about which filtering media is assembled. The filter element is mounted within a casing having an inlet for the lubricating oils. The oil is introduced into the casing under pressure and passes radially through the filter media to the central core where the filtered oil is drawn off from one end of the core. Filters for fuel, gas, air and other fluids may be similar.
It is known in such filters to provide concentric layers of different filtering media. Typically, an outer layer is formed of a relatively coarse filter material such as a wood excelsior and an inner layer is formed of a relatively fine filtering media such as a cotton fiber batt. The coarser outer layer functions to remove the large particulate contaminants and the finer material of the inner layer then filters out the smaller contaminants as the fluid travels toward the central hollow core. Examples of such filter elements are found in U.S. Pat. Nos. 3,384,241 and 4,187,136 to Wm. Nostrand.
Such filter elements will occasionally plug prematurely by reason of a build up of particulate matter towards the outer surfaces of either the coarse or fine layer. The result is that much of the filtering capacity represented by the full thickness of the filter media is not utilized before it is necessary to dispose of the filter element and replace it with a new element. A filter element in accordance with this invention prevents premature plugging by directing the oil or other fluid through the filter along flow paths that expose all portions of the filter media, both coarse and fine, to the fluid. Plugging of one area of the filter simply causes the fluid to flow to another area where fresh filter material is available until the entire filter media becomes filled with particulate matter.